1. Field of the Invention
This invention relates to a recording element unit, and a recording element driving unit, an ink jet unit, an ink jet driving unit and an ink jet device by use thereof.
2. Related Background Art
As the recording element unit to be used for an ink jet recording device, etc., for example, a recording element unit as shown in FIG. 19(a) has been known as the prior art. Also, a sectional view taken along A-A' in FIG. 19(a) is shown in FIG. 19(b).
In FIG. 19(a) and FIG. 19(b), 1501 is a holding member, 1502 is a HfB.sub.2 layer as the heat-generating resistance layer, 1503 is the common electrode of Al, 1504 are the individual electrodes of Al, 1505a and 1505b are pattern wirings of Al, 1506 is a SiO.sub.2 layer as the oxidation resistant layer and the insulating layer, 1507 is a photosensitive polyimide layer as the ink resistant layer and the insulating layer, and 1508 is a Ta layer as the cavitation resistant layer.
The recording element unit as shown in FIG. 19(a) and FIG. 19(b) passes current to the HfB.sub.2 layer 1502 as the heat-generating resistance layer, thereby generating heat energy from the HfB.sub.2 layer. More specifically, by permitting the driving current to flow into the HfB.sub.2 layer externally through the individual electrodes 1504 and the pattern wirings 1505a, and further permitting the current to flow out externally through the pattern wirings 1505b and the common electrode 1503, heat energy can be generated at the HfB.sub.2 layer. In the ink jet recording device, recording is performed by discharging liquid utilizing the heat energy.
Ordinarily, such a combination of the HfB.sub.2 layer 1502, individual electrodes 1504, and pattern wirings 1505a and 1505b (hereinafter called heat-generating element) is formed in a plural number in the recording unit 1 as shown in FIG. 19(a). Thus, by providing a plural number of heat-generating elements on the recording element unit of 1, an ink jet recording device capable of performing simultaneous recording of a plurality of dots is obtained, thereby rendering it feasible to effect a higher speed of recording. Particularly, in these days when the demands for higher density and higher speed recording are high, simultaneous recording of one main scanning line has been generalized, and therefore, recording element units having a large number of heat generating elements at high density are appearing.
In the case of performing simultaneous recording of a plurality of dots by arranging a plurality of heat generating elements on one recording element unit, the turning of the heat-generating elements on and off must be controlled individually for the respective heat-generating elements. The means for performing such control (hereinafter called the driving element) can be also formed within the recording element unit, but is generally formed on an independent substrate (hereinafter, this substrate is called the driving element substrate), and is connected to the recording element unit. This is because, when the recording element and the driving element are formed integrally, thee is the problem that if a defect occurs in a part of either of the recording element or the driving element, the whole device will fail to be actuated.
In the prior art, as the technique for bonding electrically the recording element substrate and the driving element substrate, the following techniques have been known in the prior art.
(1) The wire bonding method
The wire bonding method is a method, as shown in FIG. 20, in which the electrode 1614, 1615 of the recording element substrate 1604 is electrically connected to a desired electrode of the driving element substrate by use of an extremely fine metal wire 1616 composed, for example, of gold, etc.
(2) The method using an electrical connecting member.
This is a method in which the electrode portion of the recording element substrate is connected to the electrode portion of the driving element substrate by use of the electrical connecting member disclosed in Japanese Patent Application No. 63-133395.
FIGS. 21A to 21C are diagrams for illustration of this method. In the Figures, 1704 is a recording element substrate, 1705 is a driving element substrate, 1714 and 1715 are electrode portions, 1719 and 1720 are insulating films. 1703 is an electrical connecting member, 1717 is an electroconductive member, and 1718 is a holding member for holding the electroconductive member 1717. Here, the pitch of the electroconductive member 1717 is set narrower than the pitch of the electrodes of 1714 and 1715.
The recording element substrate 1704, the driving element substrate 1705 and the electrical connecting member 1703 are first arranged as shown in FIG. 21A, and then pressure contacted with each other as shown in FIG. 21B. FIG. 21C shows the whole view after pressure contact.
However, the electrical connecting methods of the prior art as described above have the following disadvantages.
(1) Wire bonding method:
(a) In the wire bonding method, for avoiding mutual contact between the adjacent very fine metal wires, the pitch dimension of the connecting portion on the recording element substrate or on the driving element on the driving element substrate (distance between the centers of the adjacent connecting portions) must have a certain interval. Accordingly, once the sizes of the recording element substrate and the driving element substrate are determined, the maximum number of the connecting portions will be necessarily determined. Whereas, according to the wire bonding method, the pitch dimension is generally as large as about 0.2 mm, and therefore the number of the connecting portions cannot but be small.
This means that when the number of the connecting portions of the recording element substrate or the driving element substrate is determined, the sizes of the recording element substrate and the driving element substrate must be made extremely long.
(b) The height h of the very fine metal wire measured from the connecting portion on the driving element is generally 0.2 to 0.4 mm, but since it is difficult to make the thickness thinner than 0.2 mm, no thinning can be effected.
(c) It takes a long time for wire bonding working. Particularly, when the connecting point numbers are increased, the bonding times become longer thereby reducing production efficiency.
(d) If the transfer mold conditions range is surpassed by some factors, the very fine metal wire may be deformed or even cut in the worst case.
Also, at the connecting portion on the driving element, Al corrosion is liable to occur because Al not forming an alloy with the very fine metal wire is exposed, whereby reliability is reduced.
(e) When the driving element becomes defective, it is difficult to change only the driving element.
(2) The method using the electrical connecting member.
This method has the advantages that the unit can be miniaturized, no highly precise registration is required, and the cost can be reduced, etc., but further miniaturization and cost reduction are demanded.